This invention pertains to valves, in general, and to a calibrated position indicator for a rising stem valve, in particular.
Prior art rising stem globe valves include indicators to show the position of the valve disc as a percent of full open. One such valve includes a calibrated scale mounted to a valve bonnet by means of holding screws. The valve stem extends beyond the bonnet and includes an indicator groove thereon. The scale extends above the bonnet adjacent the valve stem and includes an elongated slot through which the indicator groove may be seen. Graduated markings on the scale indicate the percent opening of the valve. To calibrate the scale the holding screws are loosened and the scale is moved upward or downward.
Such a prior art arrangement requires the use of an extended shaft and scale. Additionally, the bonnet barrel must have a flat land on which to mount the scale and must be cross-drilled and tapped for the mounting screws. Further, a packing gland and nut are used between the shaft and the valve bonnet. To remove the packing gland, it is necessary to remove or bend the scale out of the way. Once the scale has been removed or bent, zero calibration of the scale is lost.
Still further, the scale is in a fixed position relative to the bonnet and accordingly, when the valve is installed in a system, the position of the scale may be such that the scale cannot be easily read.